A pick-up truck has a cargo box used to carry various cargos. Generally, the cargo box is covered by a tonneau cover which is releasably clamped to and extended above the cargo box, so as to protect the carried cargos from adverse weather and improve the aesthetic appearance of the pick-up truck. The tonneau covers can be classified into hard-top type and soft-top type, wherein the hard-top type tonneau cover has a hard top made of rigid material, such as metal, fiberglass or the like, while the soft-top type tonneau cover has a soft top made of flexible material, such as canvas, vinyl plastic or a weather-resistant fabric. Moreover, the tonneau cover can be designed to provide a foldable function to help a user to conveniently extend or store the tonneau cover.
Referring now to FIG. 1, a perspective view of a traditional foldable tonneau cover system of a pick-up truck is illustrated, wherein a tonneau cover system 10 is used to cover a cargo box 21 of a pick-up truck 20, and the tonneau cover system 10 comprises a plurality of frame sections 11, a plurality of cover portions 12, a plurality of hinges (not-shown) and a plurality of clamps (not-shown). Each of the cover portions 12 are suitably fixed on one of the corresponding frame sections 11, and can be simultaneously folded when the tonneau cover system 10 is folded. Each of the frame sections 11 is constructed by a plurality of frame members, all of which are made of metal (such as steel, stainless steel, copper, aluminum, equivalent rigid metal or alloy thereof), engineering plastic or even wood. One of the frame sections 11 can be pivotally connected to another adjacent frame section 11 through two or more of the hinges, so that all of the frame sections 11 can be adjusted to an extended position or a storage position. When the frame sections 11 are in the extended position, the frame sections 11 are horizontally extended on two side walls 22 and a tailgate 23 of the cargo box 21, so as to cover an inner space of the cargo box 21. When the frame sections 11 are in the storage position, the frame sections 11 are folded and stacked on a front end of the two side walls 22, so as to expose the inner space of the cargo box 21. Furthermore, the tonneau cover system 10 may optionally only include a single frame section and a single cover portion 12 covering thereon, wherein the cover portion 12 can be made of flexible or rigid material.
Referring now to FIG. 2, an exploded perspective view of a corner assembly of the traditional foldable tonneau cover system from an upside-down view angle is illustrated, wherein each of the frontmost and rearmost frame sections 11 has two corner assemblies 13 for connecting adjacent frame members 111 thereof. Each of the corner assemblies 13 has a corner member 131 and a cushion member 132. The corner member 131 has two insertion portions 133, each of which can be inserted into an installation hole of the frame member 111. A connection surface 134 of the corner member 131 is formed with a plurality of ribs 135 and a plurality of cavities 136. The cushion member 132 is attached to the connection surface 134 of the corner member 131 by an adhesive tape. Moreover, the frame sections 11 further has a plurality of cushion strips 14, wherein two of the cushion strips 14 are attached to the surfaces of the frame members 111 and adjacent to the cushion member 132. The cushion strips 14 have a thickness slightly smaller than that of the cushion member 132.
Referring now to FIG. 3, an operational view of the corner assembly of the traditional foldable tonneau cover system is illustrated. When the tonneau cover system 10 is horizontally extended on the side walls 22 and the tailgate 23 of the cargo box 21, a lower surface of the cushion member 132 of the corner assembly 13 will be tightly in contact with upper surfaces of the side walls 22 (and the tailgate 23) due to the gravity and the clamping force of the clamps. Thus, the cushion member 132 of the corner assembly 13 absorbs vibration and prevents from impact between the frame section 11 and the cargo box 21 and thus reduces noise generated due to the impact.
However, there are problems existing in the actual use of the structure of the traditional corner assembly 13, as follows: Due to the gravity and the clamping force of the clamps, the lower surface of the cushion member 132 of the corner assembly 13 is tightly in contact with the upper surfaces of the side walls 22. But, after long-time repetitive use, an upper surface of the cushion member 132 facing the connection surface 134 of the corner member 131 may be deformed because the clamping force from the frame members 111 and the clamps causes the ribs 135 of the corner member 131 to press and deform the upper surface of the cushion member 132. As a result, a portion of the upper surface of the cushion member 132 sinks into the cavities 136 of the corner member 131, so as to lower the effective buffering thickness of the entire cushion member 132. If the remaining effective buffering thickness of the cushion member 132 is insufficient, the frame section 11 may be in contact with the cargo box 21 to cause impact therebetween, so as to generate noise due to the impact.
As a result, it is necessary to provide an improved corner assembly for a tonneau cover system of a pick-up truck to solve the problems existing in the conventional technologies, as described above.